1. Field
This disclosure relates generally to semiconductor devices, and more specifically, to reducing capacitance contributions due to bond pad area of a semiconductor device.
2. Related Art
Primary design considerations for power transistors used in radio frequency (RF) applications generally include output power level, reliability, stability, and efficiency. Stability, reliability and low resistance of high frequency MOSFET RF power transistors make them well suited for many RF power amplifier applications.
One consideration in designing a power transistor is minimizing generated capacitances, in order to maximize RF signal gain and minimize signal distortion. Efforts at reducing capacitances have traditionally focused on the active area of the transistor (e.g., drain-to-source capacitance and the like). But overall capacitance contributions in a power transistor comes from more than just the active area of the device, and include parasitic capacitances generated by, for example, bond pads.
Typical wire bond pads in RF transistor devices include bus bars to which wire bonds are connected. The large area of the bus bars allows, for example, flexibility in locating wire bond connections. But the large metal area of the bus bar also results in a high parasitic capacitance generated between the metalized bus bar bond pad and the underlying silicon layer of the device. Since this parasitic capacitance is directly proportional to the area of the bus bar bond pad, reducing the bus bar area can reduce the capacitance, but such a reduction will also reduce the mechanical area on which to connect a wire bond. Some traditional methods of reducing the area of the bond pad have included providing only specific areas at which a wire bond can be formed, but this limits flexibility in locating wire bonds. It is therefore desirable to provide a bond pad region that both reduces parasitic capacitance contributed by the bond pad and maintains a sufficient metallic surface region on which to form wire bonds.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.